Medicare Part A prospective payments to skilled nursing facilities (SNFs) include most of the services that outside suppliers provide to SNF residents. Pursuant to 1862(a)(18) and 1842(b)(6)(E) of the Social Security Act, outside suppliers, including ambulance suppliers, must bill and receive payment from the SNF, not Medicare, for services provided to beneficiaries in SNF stays covered under Medicare Part A. Prior Office of Inspector General reports have identified high error rates and significant overpayments for services subject to SNF consolidated billing. We will determine whether ambulance services paid by Medicare Part B were subject to Part A SNF consolidated billing requirements. We will also assess the effectiveness of edits in CMS’s Common Working File to prevent and detect Part B overpayments for ambulance transportation subject to consolidated billing.